HELP!! Customers not receiving email confirmation once booked?

I have no idea if im using this site correctly but I use bookly for the customers coming to my keep fit classes on my website, I had issues before with the email notifications, customers just werent getting them so I changed the email, now since 6am yesterday neither of us arent getting them again - Ive got 4 email addresses, ive tested each one and no emails are coming though to me even though it says sent successfully. Can anyone PLEASE help me?!! Thank you

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